1. Field of the Invention
The present invention relates to a mechanism for inserting and withdrawing a printed board unit to and from a shelf of an electronics circuit device.
2. Description of the Related Arts
In an electronics circuit device such as a communication device or an information device, a box-like shelf for accommodating a plurality of printed board units has an open-front for inserting or withdrawing the respective printed board units. A back board is fixed in the interior of the shelf and carries a plurality of female-type connectors mounted thereon. The printed board unit is inserted into the shelf along a guide rail provided on the shelf, and has at the end thereof a male-type connector insertably engageable with the female-type connector. Accordingly, the printed board unit is securely held within the shelf by the frictional force between the connectors and is electrically connected to the back board.
Recently, the mounting density of electronics parts on the printed board has been greatly increased, and thus the number of pins of a male-type connector for electric connection with the back board is correspondingly increased. This necessitates a considerable force for inserting and withdrawing the printed board unit to and from the shelf; so facilitate this operation, it was proposed in for Japanese Unexamined Patent Publication No. 62-119999, to provide a lever mechanism on the printed board.
Due to the provision of the lever mechanism, the insertion and withdrawal of the printed board unit can be easily carried out with less force, but in this mechanism, an arm of a holder member for pivotably supporting a lever is resiliently deformed; thus the pivoting position of the lever is shifted during the insertion or withdrawal of the printed board unit to and from the shelf. Therefore, the force applied on the printed board unit when connecting or disconnecting the connectors becomes unstable, and the arm of the holder member is often damaged by the repeated deformation thereof. Further, since the lever can freely rotate around the pivot when the printed board unit is not in the shelf, the lever is naturally pulled down at one end by its own weight, and thus a complicated operation such as manually holding the lever in a horizontal position when the printed board unit is fully inserted into the shelf becomes necessary. Furthermore, if the force necessary for engaging the connectors increased, it is difficult for an operator to correctly judge whether the male-type connector is completely inserted into the female-type connector, and thus the possibility of an imperfect engagement of the connectors and a resulting mis-connection is increased.
Also, because the printed board is formed by a lamination of thin plastic plates having a circuit pattern of an electro-conductive material printed therebetween, the printed board is able to bend due to the difference of heat expansion of the plastic sheets and the printed circuit during the soldering treatment. To solve this problem, a reinforcement member is fixed to the printed board, along four edges of a rectangular shape thereof, by riveting or the like, but this increases the amount of labor required, resulting in a higher manufacturing cost.